<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 层级选择器 */
        /* .box1 h1
        {
            color: red;
        } */
        /* 组合选择器 */
        /* .box1 h1,.box1 h2
        {
            color: salmon;
        } */
    </style>
</head>
<body>
    <div class="box1">
        <h1>
            hello，h1
        </h1>
        <h2>
            hello，h2
        </h2>
    </div>
    <div class="box2">
        <h1>
            hello，world
        </h1>
    </div>
</body>
</html>